Spatial Distribution of Microplastics in the Water Column of the coastal Norwegian Sea

Despite the mounting awareness of the ubiquity of global plastic pollution, annual production rates of synthetic polymers are increasing exponentially. As this global environmental problem evolves, microplastic research, focusing on plastics of the size 11 μm) in the coastal Norwegian Sea to provide comprehensible data on concentrations, polymer composition, and size classes. As part of a sampling campaign, water column samples were taken at 15 stations along the Norwegian Coastal Current (NCC) which acts as an important connector between the more densely populated lower latitudes and the Arctic. Using in situ high-volume filtration two samples of different depths and water layers were collected at each station. Sample purification was performed using an oxidative digestion followed by a density separation to remove all organic and inorganic material present. Isolated MP was subsequently identified and quantified using state-of-the-art focal plane array (FPA) based FTIR imaging technology with automated data analysis. MP particles were identified in a total of 28 out of 30 samples, with concentrations ranging from 4.33 items m-3 to 48.33 items m-3 in the upper water layer and 1.66 items m-3 to 2764 items m-3 in the lower water layer. Overall 13 different polymer types were identified, with polyoxymethylene (38 %) being the most abundant polymer in the upper water layer and polyethylene, rubber type 3, polypropylene and nitrile rubber (all ~16 %) in the lower water layer. A trend towards small MP particles was evident, with 69 % of all particles in the upper water layer and 93 % of all particles in the lower water layer being ≤ 50 μm. Among the two water layers investigated, no major differences in MP concentrations, polymer types or spatial distribution have been observed. Although comparability with other studies is hampered by the lack of harmonisation of sampling, processing and identification methods, it can be concluded that the MP contamination in the water column along the NCC are notably low